WASHINGTON – The Muslim cleric who is accused of organizing the attempted coup in Turkey also has sparked questions about the motivation behind congressional travel and charter schools in the U.S.

Fethullah Gulen, 75, lives in exile in rural Pennsylvania. But Turkey’s President Recep Tayyip Erdoğan contends Gulen was behind the attempted coup Friday that left hundreds dead and 6,000 detained, and has demanded Gulen’s extradition.

Gulen has denied organizing or knowing about the coup attempt. U.S. Secretary of State John Kerry told CNN Sunday Turkey must file a formal request and provide evidence to justify extradition that will hold up in court.

"Let's have an international committee investigate this matter," Gulen told reporters.

Gulen’s activities already have drawn attention in America. The House Ethics Committee asked the Justice Department a year ago to begin a criminal investigation of several Turkish cultural organizations that the panel said misled Congress about who paid for travel by lawmakers and staffers.

The question was whether Turkish groups had taken money from other organizations to pay for congressional travel rather than funding the trips entirely themselves. USA TODAY found about 200 trips that appeared to be improperly funded.

The groups — including the Turkic American Alliance, the Council of Turkic American Associations, the Turkic American Federation of the Midwest, the Turkic American Federation of the Southeast and the Turquoise Council — each is affiliated with a Muslim movement named for Gulen.

Members of Congress haven’t taken privately funded trips to Turkey since May 2015, according to a June review by USA TODAY, with the exception of one trip in August 2015 paid by a Norwegian group.

Congressional watchdogs said press attention dampened enthusiasm for the trips. A spokesman for the Turkish embassy said trips paid by Congress have increased while privately paid trips have declined.

Charter schools in the U.S. also have raised questions about possible ties to Gulen. A loosely affiliated group of Turkish educators organized about 100 publicly funded schools in 25 states with as many as 35,000 students, according to a 2010 investigation by USA TODAY. The schools have recruited thousands of teachers from Turkey.

School administrators said they had no official ties with Gulen. And Gulen denied any connection to the schools.